In laser direct-write (LDW) techniques, a laser beam is used to create a patterned surface with spatially-resolved three-dimensional (3D) structures by controlled material ablation or deposition. Laser-induced forward transfer (LIFT) is an LDW technique that can be applied in depositing micro-patterns on a surface.
In LIFT, laser photons provide the driving force to catapult a small volume of material from a donor film toward an acceptor substrate. Typically, the laser beam interacts with the inner side of the donor film, which is coated onto a non-absorbing carrier substrate. The incident laser beam, in other words, propagates through the transparent carrier before the photons are absorbed by the inner surface of the film. Above a certain energy threshold, material is ejected from the donor film toward the surface of the substrate, which is generally placed, in LIFT systems that are known in the art, either in close proximity to or even in contact with the donor film. The applied laser energy can be varied in order to control the thrust of forward propulsion that is generated within the irradiated film volume. Nagel and Lippert provide a useful survey of the principles and applications of LIFT in micro-fabrication in “Laser-Induced Forward Transfer for the Fabrication of Devices,” published in Nanomaterials: Processing and Characterization with Lasers, Singh et al., eds. (Wiley-VCH Verlag GmbH & Co. KGaA, 2012), pages 255-316.
LIFT techniques using metal donor films have been developed for a variety of applications, such as repair of electrical circuits. For example, PCT International Publication WO 2010/100635, whose disclosure is incorporated herein by reference, describes a system and method of repairing electrical circuits in which a laser is used to pre-treat a conductor repair area of a conductor formed on a circuit substrate. The laser beam is applied to a donor substrate in a manner that causes a portion of the donor substrate to be detached therefrom and to be transferred to a predetermined conductor location.
U.S. Pat. No. 6,155,330 describes a method of spray forming metal deposits. A spray forming pattern of a first metal, having a melting point at a first temperature, is formed with a surface defining a cavity that has the shape of a master pattern. Steel particles are sprayed onto the spray forming pattern to form a deposit on the spray forming pattern. The spraying conditions are controlled so that the steel particles coming into contact with the spray forming pattern results in a surface temperature of the spray forming pattern of less than about 80° C. The deposit and the spray forming pattern are heated to melt the spray forming pattern from the deposit. The resulting deposit has the general shape of the master pattern.